1. Field of the Invention
The present invention relates to a method and system for processing silicon materials. Particularly, the present invention is directed to a method and system for providing a thin layer of semiconductor material on a substrate and the resulting structure.
2. Description of Related Art
A variety of methods and systems are known in the art for providing a thin layer of semiconductor material on a substrate. Such methods and systems include, for example, Smart Cut™ type methods. Details concerning the Smart Cut™ method can be found in the document, “Silicon-on-Insulator Technology: Materials to VLSI, 2nd Edition,” by Jean-Pierre Colinge in “Kluwer Academic Publishers,” (e.g. at 50-51) and U.S. Pat. No. 5,374,564. Each of these documents is incorporated by reference herein in its entirety.
Such methods allow structures comprising a thin layer of semiconductor material to be produced on a support substrate, such as SeOI (Semiconductor On Insulator) type structures, in which an insulating layer is inserted between the thin layer and the support substrate. Structures obtained by such methods are utilized for applications in the microelectronic, optical and/or optoelectronic fields. Specifically, the thin layer is generally utilized as the active layer for forming components.
Stabilization of the bonding interface between the thin layer and the support substrate permits the structure obtained after detachment to have satisfactory mechanical and electrical properties. Partial solutions to this bonding interface stabilization problem have been proposed. For example, such solutions may recommend producing “strong” bonding between the donor substrate and the support substrate, typically by heat injection between the bonding and detachment steps of a manufacturing method, or even by performing a preparation treatment of one and/or the other of the surfaces to be bonded before the bonding step, such as by cleaning to improve hydrophilicity of the surface to be bonded, or polishing to produce a flat surface.
These solutions generally permit bonding to be reinforced by increasing the bonding energy between the donor substrate/thin layer and the support substrate. Bonding reinforcement is a microscopic phenomenon and bonding energy may be measured mechanically, for example according to the Maszara blade technique. A description of this technique may be found in the article, “Silicon-On-Insulator by Wafer Bonding: A Review,” by W. P. Maszara in J. Electrochem. Soc., Vol. 138; No. 1, January 1991. This article is also incorporated by reference herein in its entirety.
However, previous solutions do not allow the bonding interface to be sufficiently stabilized. Stabilization is a microscopic phenomenon that reflects the homogeneous establishment of atomic bonds (e.g., covalent bonds) between the two substrates assembled over the entire interface. The non-establishment of these bonds, even very locally, may be revealed chemically by etching by using the Wright solution. Stated another way, a stabilized bonding interface necessarily presents high bonding energy, but the inverse need not be true.
Currently, in order to produce true stabilization of the bonding interface between the thin layer of the donor material and the support substrate, a heat treatment is generally carried out on the structure obtained after detachment and transfer of the thin layer from the donor substrate to the support substrate. This treatment generally entails furnace annealing of the structure obtained after detachment at a temperature of at least 1000° C. for several hours. This type of long-duration heat treatment will be designated as “stabilization annealing” herein.
For example, in the case of SiO2/Si bonding (the layer of SiO2 is typically formed on the surface of the donor substrate being intended to play the role of the insulating layer between the thin layer and the Si support substrate), stabilization annealing typically includes exposing the structure obtained after detachment for two hours at a temperature of 1100° C. U.S. Pat. No. 6,403,450 that presents an example of such stabilization annealing. This document is also incorporated by reference herein in its entirety.
However, these partial solutions including long-duration stabilization annealing to stabilize the bonding interface is not completely satisfactory.
First, the thin layer from the donor material may not support furnace stabilization annealing for several hours. For example, such annealing applied to a thin strained silicon layer is likely to generate dislocation type defects in the thickness of the thin layer and to consequently result in relaxation of the constrained material.
Second, stabilization annealing is a long operation, typically taking several hours. This requires a significant heat budget. Also, stabilization annealing complicates the manufacturing process by taking too much time, thereby increasing the production cost of such a structure.
Third, stabilization annealing is likely, because of the installations necessary for its implementation, to degrade the quality of the thin layer on support substrate. In fact, when temperature in the thin layer exceeds 1000° C., “slip line” type defects may be produced because of the appearance of constraint zones typically located at the level of the extremities of contact points between the structure and the device (known as a “boat”) intended to support the structure in the furnace. Moreover, this thin layer quality degradation phenomenon is amplified when stabilization annealing is combined with other heat treatments, such as rapid thermal annealing, as is proposed in document U.S. Patent Publication No. 2005/0042840. This document is also incorporated by reference herein in its entirety. Such a combination, in fact, produces a succession of heat origin constraints that may finally combine to degrade the quality of the thin layer of the donor material.
As can be seen, a continuing need exists for an alternative technique to post-detachment stabilization annealing carried out at high temperatures for extended periods of time. The present invention provides a solution for these and other problems, as described herein.